1. Field of the Invention
The present invention relates to a three-dimensional modeling technique and, in particular, a process for producing a three-dimensional model involving adding a binder so as to bond a powder.
2. Description of the Related Art
There is a conventionally known technique to form a model, which is a three-dimensional model of a solid modeled object, by bonding with a binder a thin powder layer for each of a plurality of parallel cross sections of the modeled object, and sequentially layering these bonded thin layers.
Such a technique can be utilized in applications such as component prototyping, which is known as rapid prototyping, and design verification. Recently, a system employing an inkjet method, which is inexpensive, fast, and suitable for the formation of a color model, has been proposed and disclosed in, for example, Japanese registered patent No. 2729110. A specific procedure for this three-dimensional modeling is explained below.
Firstly, a thin layer of a powder is uniformly spread on a flat surface by means of a blade mechanism, and an inkjet nozzle head is made to scan and discharge a binder in a predetermined region of the thin powder layer. The powder material in the region where the binder has been discharged is subjected to an operation necessary to put it into a bonded state and also to bond it to a lower layer that has already been formed. These steps of sequentially forming a powder layer at the top and discharging the binder are repeated until the whole model is completed. Finally, powder in a region to which no binder has been applied can be removed easily when taking out the model from the equipment and the model can be separated because the powder particles are separate and not bonded to each other. In accordance with the above-mentioned operations, a desired three-dimensional model can be produced.
Furthermore, a production process employing a similar method, in which binders are colored with yellow (Y), magenta (M), and cyan (C), thus giving coloration and also improving the bonding strength, has been disclosed in, for example, JP-A-2001-150556 (JP-A denotes a Japanese unexamined patent application publication).
However, in the present situation the above-mentioned method cannot achieve a satisfactory level of properties (texture, color) for a model when compared with that which is desired. In particular, it is thought that a three-dimensional model for which transparency is required cannot be obtained by the conventional method because of the difference in properties between the powder and the binder and the presence of voids formed due to the powder. Furthermore, in order to impart smoothness to the surface, it is necessary to carry out overcoating and polishing manually, which requires the time and expense.
Moreover, it is generally difficult to reliably draw a desired pattern, etc. on a predetermined position of a three-dimensional model by hand painting.
Since a three-dimensional model immediately after forming is shaped only by virtue of the bonding force of the binder, the three-dimensional model has a low strength and, depending on the way it is handled, might be broken. Conventionally, therefore, after forming the three-dimensional model it is impregnated with a resin, a wax, etc. between the powder particles in order to increase the strength. However, such a step requires time and effort.